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Old 25th August 2003, 06:57 AM   #1
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Default Regulated power supplies in a Gainclone

Has anyone here had success with using REGULATED power supplies on a gainclone?
On his website (http://www.geocities.com/react_71/au.../gainclone.htm), Pedja says that improvements are heard using regulators, but I have seen suggestions that regulation kills the sound.
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Old 25th August 2003, 08:14 AM   #2
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As with everything else it will greatly depend upon implementation. If the regualtors are zero feedback, have a constantly low impedance way above audio and don't starve the amp for current they may well aid the sound. Building such is not trivial though.
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Old 25th August 2003, 08:21 AM   #3
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how about the capacitance multiplier
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Old 25th August 2003, 12:45 PM   #4
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I believe a regulated supply for a gainclone is unnecessary if you have nice big caps on the rails, but it can't hurt.
Do it. Enjoy it. Endure the comments from people that tell you it will/does sound awful.

/Circlotron - has built a gainclone too!
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Old 25th August 2003, 08:55 PM   #5
Pedja is offline Pedja  Serbia
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No intention to teach anyone what is good and what is bad, I just want to point out that if there are reasons for and benefits of usage of regulated supplies in line level devices, the same should be applied in power amps. By the other words, if itís wrong to use regulated supply in power amps, then regulators should be banished from CD players, preamps and similar devices. However, there are not a lot of examples of such consistency.

And of course, there are many ways to sort a regulation. For the one I suggested, typical DIYer most likely already has necessary parts, only LM338 are needed and it is done (assuming that a double bridge is already used).

Pedja
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Old 25th August 2003, 09:37 PM   #6
JoeBob is offline JoeBob  Canada
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I'm just about to slap some simple discrete voltage regulators on my chip amp, should see how it goes. The only thing is I need to buy some power resistors to use as current limiting resistors so that I don't blow my little MSR860 diodes when charging big caps, I'd rather be safe than sorry...

But with a regulator there should be a cleaner power suply, big caps and the benefits of smaller caps after the regulator. So technically it should be an improvement, now will it really? Joe said he uses regulated suplies in his amp and pedja as well reported an improvement.

So I guess all I have to do is try it and see...
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Old 26th August 2003, 03:05 AM   #7
Mikett is offline Mikett  Canada
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OK I have not built a gainclone but it sounds intriguing. However, I have built three power amplifiers with power between 100 and 300w per channel with fully regulated supplies and the difference is not subtle at all when implemeted properly.
You don't have to have monster caps in the prereg section and you don't need them after the reg either. Some good fast caps will generally do. The 1,000 uf that many use looks about right for the power range we are dealing with.

Make sure you have a reg that supplies more current than you think you'll ever need and make sure it has low output impedance into audio frequencies.

It is important that your sense line/eg output generally be very close to the device/3875. With a properly implemented reg I would not at all be surprised that the gainclones totally dispel their weak bottom end.

Be sure that the ic amp is attached to the heatsink with the lowest possible thermal resistance - that could require making sure the mating surfaces are perfectly flat. This is very important as the chip itself has very little thermal inertia/mass and will heat and current limit very quickly on bass transients. A poorly mounted device will negate the regulator effects.

This regulated gainclone thing was something I have been dreaming up for over ten years! The time might be right.
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Old 26th August 2003, 06:18 AM   #8
ukram is offline ukram  Finland
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The LM3875 has 120 dB power suppy rejection ratio (at 50 Hz), which in my opinion means there is no need for regulators.
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Old 28th August 2003, 01:01 PM   #9
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For power rail noise rejection that's certainly true, but if you want to get maximum power output you have to give it a reasonably high rail voltage of course, and under low-signal conditions this rail voltage might drift uncomfortably high. And in some places the mains voltage moves up and down a bit too. With regulation on a higher powered gainclone you don't have to give it a second thought. All depends on what you want of course. Mine for example is not regulated. +/- 33v at no load, +/- 28v full blast on 1 channel. Good enough for the application.
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Old 28th August 2003, 01:37 PM   #10
protos is offline protos  Greece
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I have been thinking that since the amp chips work so well as amps perhaps they also work well as regulators as the application notes also describe. So why not build a gainclone with the same chip as ps regulator? It is a simple and elegant solution.
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